Crosslinked polymers with low loss and tunable refractive indices

ABSTRACT

A polymer that includes a constitutional unit contributed by (a) a first monomer comprising a halocatechol diacrylate, a halocatechol diacrylate, a haloresorcinol diacrylate, or a halohydroquinone diacrylate, and (b) a second monomer comprising a charge transporting moiety.

STATEMENT OF RELATED CASES

This application is related to the following concurrently filed,commonly assigned cases, each of which is incorporated by reference: (a)Jin, “Waveguide Devices With Low Loss Clads and Tunable RefractiveIndices,” U.S. Ser. No. 11/040,819, and (b) Jin, “Process of PreparingCrosslinked, Low loss Polymers With Tunable Refractive Indices,” U.S.Ser. No. 11/041,080.

BACKGROUND

All patents, patent applications, and publications cited within thisapplication are incorporated herein by reference to the same extent asif each individual patent, patent application, or publication wasspecifically and individually incorporated by reference.

UV curable polymers have been used in the fabrication of passive andactive (e.g., electro-optic) optical waveguide devices. One of the mainadvantages of UV curable polymers is that they become solvent resistanton crosslinking, which allows subsequent polymer layers to be deposited.Additionally, UV curing can be accomplished at lower temperatures thanthermal curing, which may avoid problems like cracks or loss of adhesiondue to thermal expansion mismatches with the substrate or other polymerlayers. UV curable polymers are particularly advantageous for thefabrication of electro-optic (EO) polymer devices since avoiding hightemperature thermal curing is crucial to preserve poling induced EOactivity and the structural integrity of the chromophore. However,commercially available UV curable polymers typically are unsuitable fordeveloping commercially viable electro-optic polymer devices. Forexample, of the number of commercially available passive polymers, UV-15from Masterbond has been used for many years to fabricate electro-opticpolymer devices even though it has relatively high optical loss andundesirable mechanical strength after the fabrication process, whichprovides little protection of stacks from process damage (see, forexample, H. C Ling, et al., J Appl. Phys. 70(11), 6669 (1991); R. R.Barto, et al., ACS Poly. Mater. Sci. Eng. 83, 167 (2000); and M. -C. Oh,et al., IEEE J Sel. Top. Q. Chem. 7(5), 826, (2001). Other propertiesthat are important for electro-optic polymer devices and need to beimproved over current commercially available polymers includeconductivity around the poling temperature of the electro-optic polymercore, dielectric constant at operating temperatures and frequency, andproperties related DC bias drift.

SUMMARY

One embodiment is an optical waveguide device comprising at least onepolymer clad and a polymer core, wherein the polymer clad comprises aconstitutional unit contributed by a monomer chosen from the groupconsisting of a halocatechol diacrylate, a haloresorcinol diacrylate,and a halohydroquinone diacrylate. In another embodiment, the polymercore is an electro-optic polymer. In other embodiments, for example whenthe core polymer is an electro-optic polymer, the clad polymer mayfurther comprise a constitutional unit that includes a charge transportmoiety. In another embodiment, an optical waveguide device comprises atleast one polymer clad and a polymer core, wherein the polymer cladcomprises a constitutional unit that includes a charge transport moietyand the polymer core is an electro-optic polymer.

Another embodiment is a polymer including a constitutional unitcontributed by a first monomer and a constitutional unit contributed bysecond monomer, the first monomer comprising a halocatechol diacrylate,a haloresorcinol diacrylate, or a halohydroquinone diacrylate and thesecond monomer comprising a charge transporting moiety.

A further embodiment is a process comprising a) providing a mixtureincluding i) a halocatechol diacrylate, a haloresorcinol diacrylate, ora halohydroquinone diacrylate component, ii) a charge transportingcomponent having a radical polymerizable group, and iii) a radicalinitiator and b) initiating a radical polymerization. The materials showless electrical resistance relative to the core electro-optic polymerover a broad temperature range during the poling process, low opticalloss, and desirable dielectric constant values. Electro-optic devicesfabricated with these materials show reduced V_(π) and reduced DC biasdrift compared to devices fabricated with UV-15.

Other features and advantages will be apparent from the DetailedDescription and from the Claims.

DETAILED DESCRIPTION

One embodiment is an optical waveguide device comprising at least onepolymer clad and a polymer core, wherein the polymer clad comprises aconstitutional unit contributed by a monomer chosen from the groupconsisting of a halocatechol diacrylate, a haloresorcinol diacrylate,and a halohydroquinone diacrylate. What is meant by “constitutionalunit” and “monomer” can be found in the IUPAC Compendium of ChemicalTechnology, 2^(nd) edition 1997, published by the International Union ofPure and Applied Chemist. Preferably, the monomer is chosen from thegroup consisting of

wherein X is a halogen; R¹ is independently at each occurrence ahydrogen, a halogen, a C₁-C₆ alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4. Preferably, the optical waveguide devices furthercomprises a second polymer clad, wherein the second polymer cladcomprises a constitutional unit contributed by a monomer chosen from thegroup consisting of a halocatechol diacrylate, a haloresorcinoldiacrylate, and a halohydroquinone diacrylate. Preferably, the monomerof the second polymer clad is chosen from the group consisting of

wherein X is a halogen; R¹ is independently at each occurrence ahydrogen, a halogen, a C₁-C₆ alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4. In many embodiments, the polymer core is anelectro-optic polymer. When the core is an electro-optic polymer, themonomer of the first clad may be chosen, for example, from the groupconsisting of

wherein X is a halogen; R¹ is independently at each occurrence ahydrogen, a halogen, a C₁-C₆ alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4. Preferably, the thickness of the polymer clad isfrom about 1 μm-about 5 μm and the thickness of the electro-opticpolymer core is from about 1 μm-about 5 μm. The electro-optic core maybe in the form of, for example, a rib, trench, quasi-rib, orquasi-trench.

In other embodiments when the core polymer is an electro-optic polymer,the clad polymer may further comprise a constitutional unit thatincludes a charge transport moiety. Charge transporters are known in theart of, for example, organic light emitting diodes and may compriseelectron transporters, hole transporters, or a combination of electronand hole transporters. Preferably, the charge transport moiety comprisesa hole transporter. The hole transporter may include, for example, anamine substituted with at least two aryl groups, wherein each aryl groupmay be further independently substituted with one or more halogens,alkyl, heteroalkyl, aryl, or heteroaryl groups. Preferably, the holetransporter comprises a carbazole that may be further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups, a diphenyl amine that may be further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups; a triphenyl amine that may be further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups; or a tetraphenylbenzidine that may be furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups.

When the second polymer clad comprises a constitutional unit contributedby a monomer chosen from group consisting of a halocatechol diacrylate,a haloresorcinol diacrylate, and a halohydroquinone diacrylate,preferably the polymer core is an electro-optic polymer. Preferably, thethickness of the polymer clad is from about 1 μm-about 5 μm, thethickness of the electro-optic polymer core is from about 1 μm-about 5μm, and the thickness of the second polymer clad is from about 1μm-about 5 μm. The electro-optic core may be in the form of, forexample, a rib, trench, quasi-rib, or quasi-trench.

In another embodiment, an optical waveguide device comprises at leastone polymer clad and a polymer core, wherein the polymer clad comprisesa constitutional unit that includes a charge transport moiety and thepolymer core is an electro-optic polymer. Preferably, the chargetransport moiety comprises a hole transporter. The hole transporter mayinclude, for example, an amine substituted with at least two arylgroups, wherein each aryl group may be further independently substitutedwith one or more halogens, alkyl, heteroalkyl, aryl, or heteroarylgroups. Examples of hole transporters that include an amine substitutedwith at least two aryl groups include a carbazole that may be furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups; a diphenyl amine that may be furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups; a triphenyl amine that may be furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups; or an tetraphenylbenzidine that may befurther independently substituted with one or more halogens, alkyl,heteroalkyl, aryl, or heteroaryl groups. In other embodiments, theoptical waveguide device further comprises a second polymer clad,wherein the second polymer clad comprises a constitutional unit thatincludes a charge transport moiety. Preferably, the charge transportmoiety for the second polymer clad comprises a hole transporter. Thehole transporter may include, for example, an amine substituted with atleast two aryl groups, wherein each aryl group may be furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups. Examples of hole transporters that includean amine substituted with at least two aryl groups include a carbazolethat may be further independently substituted with one or more halogens,alkyl, heteroalkyl, aryl, or heteroaryl groups; a diphenyl amine thatmay be further independently substituted with one or more halogens,alkyl, heteroalkyl, aryl, or heteroaryl groups; a triphenyl amine thatmay be further independently substituted with one or more halogens,alkyl, heteroalkyl, aryl, or heteroaryl groups; or antetraphenylbenzidine that may be further independently substituted withone or more halogens, alkyl, heteroalkyl, aryl, or heteroaryl groups.Preferably, the thickness of the polymer clad is from about 1 μm-about 5μm, the thickness of the electro-optic polymer core is from about 1μm-about 5 μm, and the thickness of the second polymer clad is fromabout 1 μm-about 5 μm. The electro-optic core may be in the form of, forexample, a rib, trench, quasi-rib, or quasi-trench.

Another embodiment is a polymer including a constitutional unitcontributed by a first monomer and a constitutional unit contributed bysecond monomer, the first monomer comprising a halocatechol diacrylate,a haloresorcinol diacrylate, or a halohydroquinone diacrylate and thesecond monomer comprising a charge transporting moiety. Preferably, thefirst monomer is chosen from the group consisting of

wherein X is a halogen; R¹ is independently at each occurrence ahydrogen, a halogen, a C₁-C₆ alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4. In another embodiment, the charge transport moietymay be as described above.

Another embodiment is a process comprising a) providing a mixtureincluding i) a halocatechol diacrylate, a haloresorcinol diacrylate, ora halohydroquinone diacrylate component, ii) a charge transportingcomponent having a radical polymerizable group, and iii) a radicalinitiator, and b) initiating a radical polymerization. The mixture mayfurther comprise, for example, a solvent. Preferably, the solventincludes a radical polymerizable group. In one embodiment, the solventcomprises an acrylate. Preferably, the solvent comprises benzylacrylate, benzyl methacrylate, phenethyl acrylate, and phenylmethacrylate. The diacrylate component may be chosen from the groupconsisting of

wherein X is a halogen; R¹ is independently at each occurrence ahydrogen, a halogen, a C₁-C₆ alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4. Preferably, the charge-transporting componentcomprises hole transporter. The hole transporter may be as describedabove. In many embodiments, the polymerizable group of thecharge-transporting component comprises a vinyl group or an acrylategroup. The initiator in the process described above may comprise, forexample, a photoradical generator. Preferably, the photoradicalinitiator comprises acetophenone, propiophenone, or benzophenone.

In the process described above, the mixture may further comprise, forexample, a high molecular weight compound or oligomer that issubstituted with at least one acrylate or vinyl group. Examples of highmolecular weight compounds or oligomers are poly(ethyleneglycol)dimethacrylate, poly(ethyleneglycol)methacrylate, poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol)divinyl ether,poly(ethylene glycol)-bisphenol A diglycidyl ether adducttetra(methacrylate), 2,2′,6,6′-tetrabromobisphenol A ethoxylate (1EO/phenol)diacrylate, a bisphenol A propoxylate glycerolate diacrylate,bisphenol F ethoxylate (2 EO/phenol)diacrylate, bisphenol A propoxylateglycerolate diacrylate, fluorescein O,O′-diacrylate, neopentyl glycolpropoxylate (1 PO/OH)diacrylate, pentaerythritol diacrylatemonostearate, trimethylolpropane benzoate diacrylate, trimethylolpropaneethoxylate (1 EO/OH)methyl ether diacrylate, and trimethylolpropanepropoxylate triacrylate.

EXAMPLES

The following example(s) is illustrative and does not limit the Claims.

Example 1 Synthesis of 4-chloro-1,3-phenylene diacrylate.

To a solution of 4-chlororesorcinol (86.76 g, 0.60 mol) in anhydrous THF(750 mL) in a 2-liter three neck round bottom flask equipped with drynitrogen purge, thermocouple, condenser, and ice-water bath,triethylamine (163.6 g, 1.62 mol) in anhydrous THF (100 mL) was addeddropwise in 10 minutes. After 10 minutes, acryloyl chloride (136 g, 1.5mol) in anhydrous THF (300 mL) was added dropwise in 30-60 minutes(maintain 0-5 C of the solution). A precipitate formed immediately, andthe mixture was warmed to room temperature and stirred overnight (˜15hrs). The resulting mixture was filtered to remove the solid, and thefiltrate was concentrated by rotary evaporation to give a darkly coloredviscous liquid. The liquid was dissolved in methylene chloride (200 mL),cooled in an ice bath, washed with 1.0 N sodium hydroxide until pH>10,washed with 1.0 N HCl until pH<2, washed with DI water until pH>5, anddried over anhydrous sodium sulfate. The compound was purified by columnchromatography and vacuum concentrated at room temperature to give apale yellow or colorless liquid.

Example 2 Preparation of UV-Curable Liquid Comprising a HaloresorcinolDiacrylate

A homogeneous, viscous solution was prepared by combining 6.00 g of4-chloro-1,3-phenyldiacrylate (prepared above), 4.00 g of2-phenylethylacrylate, and 0.020 g of2-methyl-4′-(methylthio)-2-morpholinopropiophenone (Aldrich). Thecomposition was cured by exposure to UV light with a wavelength of 365nm under ambient conditions. The UV-cured composition has a refractiveindex of 1.550 and an optical loss <1.0 dB/cm at 1550 nm.

Example 3 Preparation of a UV-Curable Liquid Comprising a HaloresorcinolDiacrylate and a Charge Transporter

A homogeneous, viscous solution was prepared by combining 10.00 g of4-chlorophenyldiacrylate, 3.33 g of 9-vinylcarbazole (Aldrich), and 0.27g of 2-methyl-4′-(methylthio)-2-morpholinopropiophenone (Aldrich). Thecomposition was cured after exposure to UV light with a wavelength of365 nm under ambient conditions. The UV-cured material had a refractiveindex of 1.580 at 1550 nm.

Example 4 Fabrication of an Electro-Optic Polymer Waveguide

Polymer electro-optic devices were prepared by spin coating the solutionprepared in Example 3 on a six-inch silicon wafer patterned with a goldbottom electrode. The polymer was cured by exposure to 365 nm light toform an approximately 3 μm bottom clad. The bottom clad was dry etchedto provide a trench in the form of a Mach-Zehnder interferometer. Thetrench depth was approximately 0.8 μm. A solution of a nonlinear opticalchromophore (Compound 8, FIG. 3 in U.S. Pat. No. 6,750,603) in APC wasspin deposited on the bottom clad and baked in a vacuum oven to removetraces of the spinning solvent to give the waveguide core. The thicknessof the layer above the trench was approximately 3 μm. A solution asprepared in Example 3 was spin deposited on the waveguide core andUV-cured at 365 nm to give the top clad. The thickness of the top cladwas approximately 3 μm. A top electrode was deposited and the deviceswere poled to give electro-optic polymer waveguides. The devices had aV_(π) roughly one-half that of analogous devices made with thecommercial polymer UV-15LV, and the DC bias drift was much less.

Other embodiments are within the following claims.

1. A co-polymer, formed by a process comprising: reacting a firstmonomer with a second monomer; wherein said first monomer comprises ahalocatechol diacrylate, a haloresorcinol diacrylate, or ahalohydroquinone diacrylate; and wherein said second monomer comprises acharge transporting moiety.
 2. The co-polymer of claim 1, wherein thefirst monomer is chosen from the group consisting of:

wherein X is a halogen; R1 is independently at each occurrence ahydrogen, a halogen, a C1-C6 alkyl group that can be further substitutedwith one or more halogens, or a phenyl group containing at least onehalogen; and m=1-4.
 3. The co-polymer of claim 1, wherein the chargetransporting moiety comprises a hole transporter.
 4. The co-polymer ofclaim 3, wherein the hole transporter comprises an amine substitutedwith at least two aryl groups, wherein each aryl group is furtherindependently substituted with one or more halogens, alkyl, heteroalkyl,aryl, or heteroaryl groups.
 5. The co-polymer of claim 4, wherein thehole transporter comprises a carbazole that is further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups, a diphenyl amine that is further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups, a triphenyl amine that is further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups, or an tetraphenylbenzidine is further independentlysubstituted with one or more halogens, alkyl, heteroalkyl, aryl, orheteroaryl groups.
 6. The co-polymer of claim 3, wherein the holetransporter comprises an amine substituted with at least two arylgroups.
 7. The co-polymer of claim 6, wherein the hole transportercomprises a carbazole, a diphenyl amine, a triphenyl amine, or atetraphenylbenzidine.